Grease



United States Patent 3,432,431 GREASE Bill Mitacek, Bartlesville, 0kla.,assignor to Phillips Petroleum Company, a corporation of Delaware NoDrawing. Filed Mar. 14, 1966, Ser. No. 533,851 U.S. Cl. 252-16 4 ClaimsInt. Cl. Cm 5/10 ABSTRACT OF THE DISCLOSURE A grease is improved as toat least one desirable property thereof without substantially furtherthickening same by cold dispersing in the grease at least one powderedpolymer.

' This invention relates to an improved grease and the method for makingsame.

Heretofore greases have been made by thickening a suitable oil by use ofsoaps and/or by dissolving polymers in the oil at temperatures of atleast 245 F. (U.S. Patents 3,169,114 and 3,112,270 to Mitacek andGraham).

Quite surprisingly, it has now been found that the grease of US. Patents3,169,114 and 3,112,270 and other greases can be improved as to at leastone desirable property thereof without substantially further thickeningthe grease by cold dispersing in the grease, i.e. not dissolving in thegrease at temperatures of at least 245 F., at least one powdered polymerselected from the group consisting of ethylene polymers and propylenepolymers, the at least one powdered polymer being subdivided so that theaverage particle diameter, defined as that diameter whereby all thepolymer particles having smaller diameters constitute 50 weight percentof the at least one powdered polymer, is less than 300, preferably lessthan 150, still more preferably less than 100 microns.

Accordingly, the improved grease of this invention comprises a greasehaving dispersed therein in a powdered state the at least one polymer asabove defined in an amount effective to improve at least one property ofthe grease without substantially thickening same.

It is important not to excessively thicken a grease because the greasemust not be so viscous as to hinder the dispensing and/or thefunctioning of the grease. Thus, a problem solved by this invention isto improve at least one property of an already formed grease withoutfurther thickening same substantially.

Accordingly, it is an object of this invention to provide a new andimproved grease. It is another object of this invention to provide a newand improved method for making grease.

Other aspects, objects, and the several advantages of this inventionwill be apparent to those skilled in the art from the description andappended claims.

Generally, any conventional and commercially available grease isamenable to this invention. The grease employed can have been thickenedin any known manner such as by the use of soaps and/or by dissolvingpolymers in the oil at temperatures of at least 245 F., and the like.

Suitable greases includesubstantially any grade of flowable grease asdefined by the National Lubricating Grease Institute (NL'GI). Forexample, NLGI grade grease from 000 to 6 can be employed in thisinvention. Also, greases having an ASTM D 217-52T penetration at 60strokes in the range of 85 to 475 can be employed.

The lubricating oil bases which can be employed to make greases of thisinvention can be mineral, vegetable, or animal in nature, preferablelubricant bases having at least a major amount of mineral origin. Suchoils include refined oils having a viscosity of from about 35 to about240 SUS at 210 F. White mineral oil as well as other specialty oils canbe used and among the preferred oils. Paraffinic oils which producegreases of low graininess are frequently used.

Thickeners for the oils can be employed in amounts up to 20 weightpercent of the oil. Various soaps normally used to thicken greases canbe used and they include metal salts of high molecular weight acids, forexample, acids of 10 to 30 and preferably 16 to 24 carbon atoms, eithersynthetic or of animal or vegetable origin. Other carboxylic acidsuseful for making soaps of metal salts include those derived fromtallows, hydrogenated fish oil, castor oil, wool grease, and rosin.Generally the alkali metal or alkaline earth metal or aluminum or leadsalts of acids such as lauric, palmitic, oleic, stearic, and the likeare used. One of the preferred soaps is the lithium soap ofl2-hydroxystearic acid. While soaps of a general nature can be used inthe greases of this invention, it should be understood that theinvention is of use with soapless greases formed essentially frompolymers and oil alone, with or without small amounts of additives suchas rust inhibitors, antioxidants, and the like. Thus, polymers such aspolyethylene and polypropylene can be employed as thickeners, together,alone, or in conjunction with other thickeners such as soap.

In preparing the greases applicable to this invention the thickeners canbe dispersed in the oil using heat and agitation generally followed bymilling which produces shearing of the mixture, and improves propertiesof the grease such as work stability. When polymers are employed asthickeners the oil is heated at a temperature sulficiently elevated soas to dissolve the polymer in the oil. For example, when polypropyleneis used as at least part of the thickening agent, the oil is heated withstirring to a temperature of about 400 F. and stirred for from 30 to 40minutes in order to dissolve the polymer. The greases are then cooledfrom the dispersing temperature to the milling temperature or they canbe cooled to below the milling temperature and reheated either prior toor during milling, all of which is conventional in the art.

The milling can be carried out in colloid mills operated at high speedand relatively close clearance, for example, on the order of 3000 to9000 rpm. and 0.001 to 0.003 inch clearance. Any conventional greasemill can be employed. A fulland complete discussion of grease milling isfound in US. Patents 3,169,114 and 3,112,270, the disclosures of whichare incorporated herein by reference.

Other materials normally used in greases can also be employed in thegreases applicable to this invention. For example, additives such asrust inhibitors, antioxidants, fillers, pigments, perfumes and the likecan be employed. Some examples of such materials includepropylenediamine, phenyl-ot-naphthylamine, phenothiazine, mica,asbestos, powdered lead, powdered zinc, talc, alumina, titanium dioxide,molybdenum, disulfide, bentones, carbon black, nitrobenzene and thelike. Generally, the amount of these modifiers is less than about 10percent of the total weight of the grease.

The sub-divided polymers employed according to this invention arepreferably homopolymers of ethylene, homopolymers of propylene, andnon-rubbery copolymers of ethylene and propylene. Mixtures ofhomopolymers and/ or copolymers can also be employed. The ethylenepolymers used in this invention are high density polymers, i.e. have adensity at 25 C. of at least 0.94 grams per cubic centimeter. Thepropylene polymers can have a density at 25 C. of from 0.890 to 0.920gram per cubic centimeter. The amount of sub-divided polymerincorporated in the grease will generally be in the range of from about0.1 to about 10, preferably from about 0.5 to about 5, weight percentbased on the total Weight of the greases.

Although any procedure giving equivalent results can be used, apreferred density determination method for the polymers employed in thisinvention is set forth in U.S. Patent 3,112,270, column 2, lines 39-64.

The ethylene polymers employed in this invention can include copolymersformed of ethylene with at least one other olefin of higher molecularweight, e.g. up to 8 carbon atoms per molecule. Examples of suitablecomonomers include propylene, l-butene, Z-butene, l-pentene, l-octene,4-methyl-l-pentene, 4-methyl-1-hexene, fi-methyl-l-heptene,4-ethyl-1-hexene, and the like. Preferred copolymers include ethylenewith propylene or l-butene. In general, ethylene makes up at least 95weight percent of the copolymer. In forming such a polymer the monomerfeed to the polymerization zone will ordinarily be at least 80 percentby weight ethylene. As the percent of ethylene in the copolymer isdecreased the density of the polymer likewise is decreased 50 that thedensity limitation can be used as an indication of copolymercomposition. In other words, if the density of the ethylene-containingcopolymer is 0.940 or above, it will be suitable for the invention. Thepropylene polymers include copolymers as defined hereinabove forethylene polymers including the propylene making up at least 95 weightpercent of the copolymer. The melt index of the propylene polymer canvary widely; for example, from about 0.1 to about 25, preferably from 1to 6 as determined by ASTM D 1238-62T, Procedure E.

The sub-divided polymers will have an average particle diameter asdefined hereinabove. By average particle diameter it is meant thediameter of the particle if it is substantially spherical in which casethe length, breadth, and thickness of the particle are all substantiallyequal. However, when the particle is irregular in external configurationso that the length is greater than the breadth and the breadth isgreater than the thickness, the average particle diameter is taken to bethe breadth since it is the intermediate dimension and it is thisintermediate dimension which is generally the controlling medium insieving and is almost always visible under the microscope. The averageparticle diameter whereat all those particles in the sub-divided polymerwhich have a smaller average diameter add up to 50 weight percent of thetotal weight of the sub-divided polymer can be obtained in anyconventional and Well known manner such as by sedimentation, electronicanalysis, or visual techniques such as the ASTM technique designatedE20-51T and entitled Analysis by Microscopical Methods for Particle SizeDistribution of Particulate Substances of Sub-Sieve Size. From theseanalysis techniques a plot can be made employing weight percent as theordinant and particle diameter as the abscissa so that the particularparticle diameter at which 50 weight percent of the sample is made up ofparticles having smaller diameters can be readily determined.

The sub-divided polymer or polymers can be incorporated into the greaseby conventional blending machines, as in grease manufacturing discussedhereinabove. The incorporation of these sub-divided polymers must becarried out at temperatures below that which allow melting and/ordissolving of the polymer in the grease. In other words, the temperatureof dispersion should be that which allows dispersion and retention ofthe polymers in the grease in the sub-divided, solid state. Generally,the dispersing operation should not be carried out at a temperaturesubstantially exceeding 225, preferably 200 F. Good dispersions can beobtained by operating substantially at room temperature.

Example I Powdered polyethylene (Microthene 608) having an averageparticle diameter as defined above of less than 74 microns wasincorporated into two greases in the amount of 1 weight percent based onthe total weight of the grease. The powdered polyethylene was obtainedfrom polyethylene having a density of 0.96 gram per cubic centimeter at25 C. (ASTM D 1505-63T) and a melt index of 19.5 grams/10 minutes, (ASTMD 1238- 62T, Procedure E). The first grease, grease A, was prepared fromsolvent refined neutral Mid-Continent base oil of about 75 SUS at 210 F.which had been thickened with about 12 weight percent based on the totalweight of the grease of mixed lithium fatty acid soaps of mixedeven-numbered fatty acids whose carbon atom range per molecule variedfrom 14 to 22. The second grease, Grease B, was prepared from a solventrefined neutral Mid-Continent base oil of about 500 SUS at 100 F., aviscosity index of about 89. Grease B had been thickened by dissolvingin the oil 1 weight percent based on the total weight of the grease ofhigh density polyethylene (the pellets having a density of about 0.96and a melt index of about 5) and by 9 Weight percent based on the totalweight of the grease of a soap formed by saponifying a mixture of 3parts methyl l2-hydroxystearate and 1 part of castor oil with astoichiometric quantity of lithium hydroxide.

Grease A was formed by adding the soap-forming ingredients to the oiland heating the mixture to about 400 F. with agitation followed bycooling and milling at about 180 F. Grease B was formed by adding thehigh density polyethylene and the soap-forming ingredients to the oiland heating the mixture to about 400 F. with agitation followed bycooling and milling at about 180 F.

The powdered polyethylene was incorporated in separate portions of bothgreases A and B by blending in a Hobart mixer at about 75 F. for about60 minutes.

Grease A and Grease B both with and without powdered polyethyleneincorporated therein were then tested and the results were as follows:

TAB LE I n+1 wt. B+1 wt. percent percent Grease A powdered B powderedpolyethpolyethylene ylene ASTM penetration, 60 strokes 273 281 272 265Tlmken endurance, minfl. 3 72 5 7 5 Wheel bearing tests, grams leakage:

ASTM test 3 0.7 0. 4 Phillips modified test 4 15. 6 15. 1

Example II Several samples of a Mid-Continent solvent refined neutraloil which had a viscosity of 500 SUS at F. and a viscosity index ofabout 80 were thickened using varying amounts of conventional highdensity pelleted polyethylene having a density of about 0.96 gram percubic centimeter at 20 C. (ASTM D 1505-63T) and a melt index of about 5grams/ 10 minutes (ASTM D 1238- 62T, Procedure E), and using in eachsample the same amount of a soap formed by saponifying a mixture of 3parts of methyl 12-hydroxystearate and 1 part castor oil with astoichiometric quantity of lithium hydroxide.

In Run 1 the oil was thickened into grease by adding 9 weight percent ofthe soap based on the total weight of the grease, the oil and soap beingmixed with heating until the temperature reached 400 F. after a periodof about 1 hour, 45 minutes.

In Run 2 the oil was thickened with 9 weight percent soap in the samemanner as Run 1. To the grease of Run 2 was added 1 weight percent basedon the total weight of the grease of powdered polyethylene having anaverage particle diameter of less than 74 microns and formed from thesame polyethylene as defined in Example I. The powdered polyethylene wasincorporated in the resulting grease by agitation at room temperaturefor about 60 minutes.

In Run 3 the oil was thickened with 9 weight percent soap based on thetotal weight of the grease and 1 weight percent of the pelletedconventional high density polyethylene thickening agent by adding thepelleted polyethylene simultaneously with the soap forming ingredientsand heating, cooling, and milling as with Run 1. Thus, in Run 3 thepelleted polyethylene added was dissolved in the hot base oil as opposedto the powdered polyethylene in Run 2 being dispersed in cold base oiland retaining its original particulate form.

In Run 4 the oil was thickened by the high temperature incorporation of9 weight percent soap and 2 weight percent conventional high densitypelleted polyethylene using the same method as Run 3.

In Run 5 the oil was thickened by the high temperature incorporation of9 weight percent soap and 1 weight percent conventional high densitypelleted polyethylene using the procedure of Run 3 and thereafter Iweight percent of powdered polyethylene was incorporated in theresulting grease at room temperature using the same method as Run 2.

Thus, in Runs 4 and 5 the same amount of polyethylene was present in theresulting grease. However, for Run 4 all the polyethylene was dissolvedin oil during the preparation of the grease and for Run 5 half thepolyethylene was present in the resulting grease in substantially theoriginal particulate state. A table of the thickeners and powderedpolyethylene present in the greases of Runs 1 through 5 is presented inTable II.

The greases from Runs 1 through 5 were tested with results as follows:

TABLE III ASTM Timken Apparent viscosity Run No penetration, Endurance,at 20 F., poise,

60 strokes 1 mini shear rate 200 sec: 3

1 ASTM D 217-521.

2 NLGISpokesman, Vol. XX, No. 9, p. 36 (1956), 7.5 lb. load.

8 ASTM D 1092452.

From Table HI a comparison of Runs 2 and 3 with Run 1 shows that withthe grease having powdered polyethylene therein according to thisinvention, Run 2, the hardness of the grease was substantially the same(all falling in the NLGI range for grade 2 grease) while the lubricationendurance of the grease of Run 2 was substantially improved over that ofthe greases of Runs 1 and 3. Similarly, a comparison of Runs 1, 4, and 5shows that the' grease according at this invention, Run 5, hadsubstantially the same hardness as the other greases but also asubstantially improved lubrication endurance over the greases of Runs 1and 4. Thus, it is apparent that the improved results of this inventionare obtained from the presence of this particulate, cold-dispersedpolymer in the grease. Further, the higher apparent viscosity of thegreases of Runs 3 and 4 show that those greases did not flow as well asthe greases of this invention, i.e. Runs 2 and 5. Also, comparison ofRuns 2 and 3 and Runs 4 and 5 show that the invention Runs 2 and 5 haveadvantageous apparent viscosities. Thus, the invention offers a newmeans for incorporating greater quantities of desirable polymer into agrease and enjoying its beneficial influence on lubricity yet withoutsubstantially changing the hardness (grade) or viscosity of the grease.

Reasonable variations and modifications are possible within the scope ofthis disclosiure without departing from the spirit and scope thereof.

I claim:

1. An improved grease consisting essentially of at least one polymerselected from the group consisting of ethylene polymers and propylenepolymers in a sub-divided, substantially solid, dispersed state, said atleast one polymer being present in an amount elfective to improve atleast one property of said grease without substantially thickening same,said at least one polymer being sub-divided so that the average particlediameter, defined as that diameter whereat all the polymer particleshaving smaller diameters constitute 50 Weight percent of said at leastone polymer, is less than 300 microns, said at least one polymer isdispersed in said grease at a temperature not greater than 225 F. toprevent melting and dissolving of said polymer, and said polymer ispresent in the amount of from about 0.1 to about 5 weight percent basedon the total weight of the grease.

2. The grease according to claim 1 wherein said grease is formed from atleast one grease having an ASTM D 217-52T penetration at 60 strokes inthe range of to 475, said at least one polymer is present in the rangeof from about 0.1 to about 10 weight percent based on the total weightof the grease, and said at least one polymer is selected from the groupconsistig of polyethylene having a density at 25 C. of at least 0.94gram per cubic centimeter, and copolymers of ethylene and l-olefinshaving a density at 25 C. of at least 0.94.

3. The grease according to claim 1 wherein said at least one polymer isa homopolymer of ethylene having a density at 25 C. of at least 0.940gram per cubic centimeter, said polyethylene is dispersed in said greaseat about room temperature and is present in the amount of from about 0.1to about 5 weight percent based on the total weight of the grease, theaverage particle diameter of the polyethylene in said grease is lessthan microns and said grease was formed at least in part by dissolvingat least one polymer in the base oil.

4. The grease according to claim 1 wherein said at least one polymer isa homopolymer of propylene having a density at 25 C. of at least 0.89gram per cubic centimeter, said polypropylene is dispersed in saidgrease at about room temperature and is present in the amount of fromabout 0.1 to about 5 weight percent based on the total weight of thegrease, the average particle diameter of the polypropylene in saidgrease is less than 100 microns, and said grease was formed at least inpart by dissolving at least one polymer in the base oil.

References Cited UNITED STATES PATENTS 2,791,576 5/ 1957 Field et al.25259 2,810,695 10/1957 Young et al. 25228 2,887,472 5/1959 Fotis 252-592,917,458 12/1959 Morway et al 25259 3,080,330 3/1963 Rudel et a1 252593,112,270 11/1963 Mitacek et al 25259 3,114,708 12/1963 Morway et a125212 3,169,114 2/1965 lMitacek et al. 25259 3,216,935 11/1965 MOP-Wayet al 25259 3,271,311 9/1966 Morway et al. 25259 3,290,244 12/ 1966Polishuk et al 25259 PATRICK P. GA-RVIN, Primary Examiner. I. VAUGHN,Assistant Examiner.

U.S. Cl. X.R. 25217, 59

